Dog Addison’s disease is sometimes called ‘the great pretender’ because its symptoms — lethargy, vomiting, weight loss, weakness — mimic dozens of other conditions. Many dogs are misdiagnosed repeatedly before the true cause is identified. Once diagnosed, however, Addison’s disease is very manageable, and most dogs go on to live completely normal lives with appropriate treatment.
What Is Addison’s Disease in Dogs?
Addison’s disease, or hypoadrenocorticism, occurs when the adrenal glands stop producing sufficient amounts of two critical hormones: cortisol (a glucocorticoid that helps the body respond to stress and regulates metabolism) and aldosterone (a mineralocorticoid that controls sodium, potassium and fluid balance). In the primary form the immune system attacks and destroys the adrenal cortex. Secondary Addison’s disease occurs when the pituitary gland fails to produce enough ACTH. Atypical Addison’s involves only glucocorticoid deficiency.
Symptoms of Addison’s Disease
Because cortisol and aldosterone affect virtually every body system, symptoms are broad and waxing-waning. Common signs include episodic weakness or exercise intolerance, vomiting and diarrhea (often bloody), loss of appetite and weight loss, shaking or trembling, increased thirst and urination, abdominal pain, mental dullness, and slow heart rate from elevated potassium. Symptoms worsen during stressful events — travel, boarding or illness can trigger a flare.
The most dangerous presentation is the Addisonian crisis: sudden cardiovascular collapse with vomiting, diarrhea, weakness, and shock that is fatal without immediate treatment. Any dog with unexplained collapse or recurrent GI illness should be evaluated for Addison’s.
Causes and Diagnosis
Most primary cases result from immune-mediated destruction of the adrenal cortex; a genetic predisposition exists in several breeds including Standard Poodles, Nova Scotia Duck Tolling Retrievers, Portuguese Water Dogs, Great Danes and Bearded Collies. Diagnosis requires an ACTH stimulation test: cortisol levels measured before and after synthetic ACTH injection show little or no rise in Addisonian dogs. A low sodium-to-potassium ratio on bloodwork is a classic red flag that often prompts the test.
Treatment of Addison’s Disease
Lifelong hormone replacement is required. The standard protocol uses desoxycorticosterone pivalate (DOCP) injections once every 25–28 days to replace aldosterone, combined with daily low-dose prednisone to replace cortisol. An alternative is daily oral fludrocortisone, which replaces both hormones. During illness, surgery or major stress, dogs need a ‘stress dose’ of prednisone — typically two to five times the normal daily amount — to prevent crisis. An emergency supply of injectable dexamethasone is recommended for owners comfortable giving injections.
Long-Term Management and Prognosis
The prognosis is excellent once the condition is well-controlled. Bloodwork every six to twelve months guides DOCP dose adjustments based on electrolyte levels. Owners should carry a medical alert card for their dog noting the diagnosis and medications. Travel, boarding and elective procedures require advance coordination with the vet for appropriate stress dosing. With consistent treatment and monitoring, dogs with Addison’s disease enjoy a completely normal quality and length of life.